diff --git a/kws/utils/executor.py b/kws/utils/executor.py
index 51fc529..94a7270 100644
--- a/kws/utils/executor.py
+++ b/kws/utils/executor.py
@@ -50,6 +50,7 @@ class Executor:
             grad_norm = clip_grad_norm_(model.parameters(), clip)
             if torch.isfinite(grad_norm):
                 optimizer.step()
+            optimizer.zero_grad()
             if batch_idx % log_interval == 0:
                 logging.debug(
                     'TRAIN Batch {}/{} loss {:.8f} acc {:.8f}'.format(